This invention relates to a tonearm linear-drive apparatus, and, more particularly to such apparatus wherein a linear-drive force for the tonearm is derived from at least a portion of gravity.
In a pivoted arm system in which the tonearm is rotated about its pivotal point which is stationary in position with respect to the rotating axis of the disc, it is known that, since the disc has a sound groove thereon which has been formed upon cutting of the master record disc by driving the cutter head linearly across the master record disc, various disadvantages including generation of tracing distortions, for example, appear when such record disc is re-produced.
In order to overcome above disadvantages, a tonearm linear-drive system was developed wherein the pivotal point of the tonearm was moved in response to the movement of the stylus tip due to pulling force by the groove of the rotating disc so as to permit the stylus tip to move linearly across the disc. In this prior system, the pivotal point of the tonearm was designed to linearly move step by step with small increment of the stylus tip movement toward the center of the disc, because the speed of such stylus tip movement is not constant in time. This linear movement of the pivotal point of the tonearm was carried out by using an electric motor.
Therefore, one object of this invention is to provide means for permitting the pivotal point of the tonearm to linearly move in the same manner as in the prior art system, without using an electric motor or any other driving source.
The other object of this invention is to provide means for causing step by step linear movement of the pivotal point of the tonearm in very simple manner.